I disagree. I would take any advice from an aquaria site such as the
krib with a grain of salt- the goals of aquaria and biospheres are
fundamentally different so a lot of the advice is not applicable or
wrong. Aquariums have a high biomass load and minimal nutrient
cycling so a lot of maintenance is required to manage that biomass
(mainly by removing it during water changes). The main animals in
aquaria are fish. Biospheres have low biomass, rapid cycling, and the
main animal are small invertebrates- there are less of them (think of
how many brine shrimp it takes to equal the weight of even a small
fish), they are probably less metabolically active and differ in
their sensitivities to contaminants. This all impacts some of the
issues you bring up:

Chlorine: the sulfur compounds and other chemicals you used to
dechlorinate are going to be in your biosphere forever- I don't know
what will happen to them overtime or how they effect invertebrates
but why risk it? As someone else said it is simpler to filter the
water and then let the chlorine gas out over a couple of days.

Nitrates: Has anyone ever tested for them in a biosphere? I'd be
really surprised if this is a problem in biospheres. The organisms we
are talking about are going to secrete their waste mostly as ammonia,
the ammonia is going to be gobbled up by the algae/plants which use
it as nitrogen source. If you don't have enough plant growth to deal
with the nitrogen your animals are going to die from lack of oxygen
long before there is enough waste to be a problem. Remember you are
not adding more nitrogen in the form of food- whatever nitrogen you
started with is all there is. The traditional aquarium nitrogen cycle
(which is not really a cycle) would be counterproductive because it
would tie up nitrogen in the substrate and reduce its availability to
plants.

Trace elements: This is what eventually kills the commercially
biospheres- elements needed by either the plants or shrimp get stuck
in forms that aren't usable and are lost out the system permanently
but it takes a couple of years. In the short term it is less of a
problem.

What kills biospheres: Lack of plant growth (a lot of people on here
have had that problem but I'm not sure why). temperature extremes, pH
problems

> make. I did a lot of research, and concluded that a self contained
> biome is impossible to sustain indefinitely, and very difficult to
> sustain for any extended length of time.

I guess it depends on what you mean by indefinitely there are closed
ecosystems set up in the 1970s that are still alive. The commercially
available ones can last years- people on this list have had ones that
last months (any updates?). I think the most luck has been had with
organisms harvested in the environment.

--- In homemadebiospheres@yahoogroups.com, "capntao" <capntao@y...>
wrote:
> Besides what Phillip said, I would consider a few things necessary.
> First, read up on water chemistry, nitrogen cycles, and other
> important fields, as well as fish and water plants, at
> http://www.thekrib.com and be sure to view the beginner aquarium
> tips page at above site, which is located at
> http://faq.thekrib.com/ . This should give you a good background,
> and give you some expectations and goals to help your creatures
> survive. Be sure not to use straight tapwater, as the chlorine
would
> be devastating to any life attempting to get a foothold in your jar
> or tank, especially the all important bacteria. Get some
> dechlorinating tablets,

Another thing to consider is the fact that most
> of your creatures will die, usually in a stressful and miserable
> fashion, due to the (probably) inevitable buildup of nitrates, as
> well as consumption of trace elements, that a closed system causes.
> Personally, I have given up my plans for a biosphere, at least
until
>!